The present invention relates to a magnetophoretic display panel in which magnetic particles encapsulated in the panel migrate due to magnetophoresis under the action of a magnetic field, to thereby effect display and erasure.
There has heretofore been known a method of display by using a magnetic panel having a multi-cell structure formed between two substrates and in which a liquid dispersion comprising magnetic particles, a dispersion medium, a coloring agent and a thickening agent is encapsulated in the cells between the two substrates, wherein the magnetic particles migrate due to magnetophoresis from the bottom of the magnetic panel as they are attracted toward the surface of the magnetic panel by the action of a magnetic field produced by a magnetic pen for recording, to thereby produce the display relying upon a difference in color between the dispersion medium and the magnetic particles, as disclosed in, for example, Japanese Patent Publications Nos. 47676/1984 and 46439/1982, Japanese Utility Model Publication No. 35356/1981, and Japanese Patent Laid-Open Publication No. 183291/1996.
Various properties of the magnetic particles encapsulated in the magnetic panel have been disclosed in Japanese Patent Publication No. 7532/1996.
The display and erasure on the magnetic panel are determined by:                (1) a thickness of the panel;        (2) an effective magnetic flux density when the recording or erasure magnet is slid on the upper surface or the lower surface of the panel;        (3) magnetization of the magnetic particles when the so-called low magnetic field is acted upon corresponding to the effective magnetic flux density of the magnet stated in (2) above; and        (4) a viscosity of the liquid which is a dispersion medium.        
Unfortunately, the problem cannot be solved by only the individual factors described in the above publications, such as saturation magnetization of the magnetic particles, thickness of the panel, flux density of the magnet, etc.